Sirtuin
Definition
A family of NAD-dependent enzymes that modify proteins involved in metabolism, DNA repair and stress response. They are the usual mechanistic hook for claims made about NAD precursors.
What this means for research sourcing
Mechanistic terms like this describe how research compounds behave in vitro. See the mechanism overviews for compounds Volta stocks.
Related Terms in Pharmacology
NAD+ (Nicotinamide Adenine Dinucleotide)
The central redox cofactor in every living cell, carrying electrons through energy metabolism and acting as a substrate for the sirtuins and PARP enzymes. It is a nucleotide rather than a peptide, and it is grouped with research peptides for commercial reasons rather than chemical ones.
Telomerase
The enzyme that rebuilds telomeres and so offsets the shortening that comes with each division. Epithalon is studied for effects on its activity, with human cell-culture work from Khavinson and colleagues in 2003, rodent studies and Russian clinical reports, and no Western randomised trial.
IC50
The concentration producing half of the maximum inhibition in a given assay. It is assay-dependent rather than a constant of the compound, so IC50 values are comparable only when the conditions behind them are.
Dissociation Constant (Kd)
The concentration at which half the available binding sites are occupied at equilibrium. A lower value means tighter binding, and unlike IC50 it describes the interaction rather than the readout used to measure it.
Uptake
Movement of a substance from outside a cell or compartment to inside it, whether passively or by a transporter. It is measured in a defined system, and an uptake result in cultured cells does not establish what happens in an organism.
Bioavailability
The fraction of an administered amount that reaches the circulation intact and is therefore available to act. Intravenous delivery is 100% by definition; everything else is measured against it.
Oral Bioavailability
Bioavailability by mouth, which for most peptides is under 1%: gastric acid and intestinal proteases degrade them and the surviving fraction struggles to cross the epithelium. Overcoming it takes permeation enhancers, enteric protection or a very short sequence.
Half-Life
The time taken for the amount in the body to fall by half. It sets how often a compound has to be given and how long elimination takes, about four to five half-lives for the bulk of it to clear.